1. Field of the Invention
An embodiment of the present invention relates to the encoding and/or decoding of audio signals, and more particularly, to a system, medium, and method encoding/decoding a multi-channel audio signal.
2. Description of the Related Art
Examples of a general audio coding include a waveform multi-channel audio coding and a parametric multi-channel audio coding. In the waveform multi-channel audio coding, 5 audio channel signals may be received and 5 audio channel signals may be output. Examples of the waveform multi-channel audio coding include an MPEG-2 MC audio coding, an AAC MC audio coding, and a BSAC/AVS MC audio coding, for example. The MPEG-2 MC audio coding is executed in two types of modes, one of which is a mode operated on original signals and the other is a mode operated on two downmixed signals and other independent signals, the AAC MC audio coding is executed on original signals with PCE and default settings, and the BSAC/AVS MC is a bit sliced arithmetic audio coding executed on original signals with channel_configuration_idx.
An example of the parametric multi-channel audio coding includes an MPEG surround coding that decodes 1 or 2 input channel signals into 5 or 6 channel signals. In addition, the MPEG surround coding is based on Quant Matrix Extention (QMF), a reverse one-input to two-output decoding tool (R-OTT), a reverse two-input to three-output decoding tool (R-TTT), and a R-OTT tree regarding extended signals. Here, as an example, a one-input to two-output tool is a tool that takes one input and generates two outputs.
FIG. 1 illustrates such an MPEG surround decoder. There are various speaker configurations at the receiver sides of decoders, for example, 1, 2, 3 (front)/0(rear), 3/1, 3/2, and 5/2. Hence, the input encoded audio bitstream can be decoded into all available audio channel signals which can be selectively chosen for output depending on the speaker configuration used at the receiver side of a decoder.
Similarly, FIG. 2 illustrates a corresponding encoder for encoding the input audio channel signal into the audio bitstream and a decoder for decoding the encoded audio channel signal. In the case of MPEG surround, the encoder encodes M input audio channel signals and outputs N audio channel signals, as the audio bitstream, with M being greater than N. The decoder may then decode the N encoded audio channel signals and output L decoded audio channel signals, with L being greater than or equal to N, and M being greater than or equal to L.
However, in such conventional decoders, the L audio channel signals are directly generated by decoding M input audio channel signals (e.g., when M=N=L) or by an upmixing of downmixed M input audio channel signals into N audio channel signals and then decoding the N audio channel signals. However, it is difficult to decode input audio channel signals into audio signals of a suitable number of channels based on the actual known type of a speaker configuration at the receiver.